Synchronous telegraph system



June 1l, 1929. (3, A, L OCKE sYNCHRoNoUs TELEGRAPH SYSTEM Filed July 14, 1927 2 Sheets-Sheet .S Jl kmkm ML SQSR. h5 SSW. MMM 1 r Tl# H H H H Q Q /N VEN o R 550,965 A L oc/ff June 11, 1929. G. A. LOCKE SYNCHRONOUS TELEGRAPH SYSTEM 2 Sheets-Sheet Filed Jul,r 14'A 1927 Tron/v5 Y Patented June 1l, 1929.

UNITED STATES A V1,717,049 PATENT OFFICE.

. GEORGE A. LOCKE, OF GLEN COVE, NEW YORK, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION F NEW YORK.

SYN CHRONOUS TELEGRAIH SYSTEM.

Application led July 14,

This invention relates to synchronous signaling systems and particularly to synchronous telegraph systems adapted for transmlssion alternately in each direction.

A broad object of the invention is to insure the proper synchronization of sending and' receiving equipment before the transmission of signaling impulses is begun. A more specific object is to synchronize transmitting and receiving stations in a system following a reversal of the direction of transmission.

. In a synchronous telegraph system adapted for transmission alternately in each direction, there is ai period of time following the cornpletionof transmission in one direction and preceding the resumption of transmission in the reverse direction when no correcting impulses are transmitted over the line. At such Ytimes the two distributors may tend to fall out of synchronism and although the time occupied in reversing the direction of transmission is-of brief duration the distributors at different stations may drift out of phase suiiiciently to require lseveral corrections to restore them to their proper relative positions, and they may be sufficiently out of phase to interfere with the proper reception of signaling impulses for the brief period before the correcting mechanism has restored 'synchronism l This invention eliminates the ditliculty de- .scribed above by the use of automatic switching means to lock up the transmitting and receiving apparatus following reversal of direction, while transmitting synchronizing impulses for a brief period to restore the receiving stationto synchronism with the transmitting station. l

Referring to the drawings, Figs. 1 and 2, when arranged side by side with Fig. 1`on the left, disclose the arrangement-of apparatus'at a telegraph station incorporating applicants invention. This station will hereafter be known as station B and a similar station at a dist-ant point on the line conductor will be known as station A.

y Briefly,-as` illustrated in the drawing, the invention comprises directionreversing switches operated by cams 37, 38, and 36 for connecting or disconnecting the line conductor 1 to the transmitting distributor or a receiving distributor, shown in the upper and lower parts of Fig. 1, respectively, and for properly conditioning the receiving and 1927. Serial No. 205,544.

transmitting equipment before and after each line switching operation so that no signal yimpulses are lost or mutilated.

Referring to the drawing in detail, a line conductor 1,-which in this case is shown as a` submarine cable, is connected to armature 4 of a switching relay 2, which serves-to connect it to either sending apparatus or receiving apparatus under the control of switching cam 36. Rectangle 6 represents a receiving shaping network and amplifier andv since a detailed knowledge of that apparatus is not necessary for a full understanding-of the present invention, its position in the circuit has merely been indicated. For a complete description of a shaping network and amplifier of this type applicant is referred to a copending application of A. M. Curtis, Serial No. 119,537, filed June 30, 1926. In the output of the amplifier circuit are shown two polar relays 8 and 9 which serve to repeat received impulses to the receiving distributor ring 26 and the synchronous correcting mechanism represented by rectangle 12, respectively. Synchronous driving and correcting apparatus which is suitable for use in a system of this type, is disclosed inv the above mentioned application, 'Serial No. 119,537, and also in applicants copending application Serial No. 123,328,'iled July 19, 1926. In brief, the synchronous correcting mechanism comprises means for automaticallyorienting the distributor shaft 65, which revolves the brushes 16, 19, 85 and 28 over their respective segments through gears 63 and shaft 64, to maintain the brushes at the receiving station exactly in phase with the distributor brushes at the transmitting station. In practice, it is customary to set the distributor driving motors at the two stationsv shaft at the receiving station is required to maintain it in synchronism with the distant transmitting distributor. 14, 15, 17, 18, 59, 60, 26 and 27 represent rings on the synchronous distributor. These would ordinarily be arranged on a circular face, but foi` convenience are shown in the drawings as developed into a plane surface. Of these rings, 14 and 15 controlvthe rotation of shaft 57 and the automatic switching cams which reverse-the direction of transmission. Rings 17 and 18 are the transmitting rings, each segment of the transmitting and receiving equipment for only two channels is shown.

Considering the impulse transmitter for channel 1, which is shown enclosed in dotted rectangle 61; 69, 70, 71, 72, and 7 3 represent :tongues arranged to be operated by a perforated tape. When transmitter control magnet 21 is released, the tongues move under controlof the tape and retain their positions until magnet 21 energizes ywhen the tongues are restored to their normal position (closed o n their left contacts as shown) and the transmitting tape is advanced to the next position. It should be noted that as long as magnet 21 is energized the transmitting tape is held stationary and the transmitting tongues are held locked against their left contacts. A

diere'ntial relay 20 operates in response to current in one of its windings, but is not.

affected by current iowing in both of them. Ordinarily, during a transmitting period, conductors 25 and 23 are short circuited through contacts 49 on cam 38 and, therefore, relay 2O Icannot operate. Whenever contacts 49 are opened, however, no current y can fiow through the right winding of relay 20, which thereupon locks up to contact 24 and holds magnet 21 operated until contacts 49, operated by cam 38, again close. The dotted rectangle represents the transmitter in channel 2. It is similar in all respects to the apparatus in channel 1, except that the left contacts of the transmitting tongues arel conneced to negative battery instead of positive, and the right contacts are connected to positive instead of negative. Likewise, the control magnet and diHerential relay are controlled from contacts 50 operated by cam38. The transmitting equipment in channels 3 and 5 is identical with that in channel 1 and the equipment in channel 4 is identical with that in channel 2. The transmitters for the 'last three channels are controlled, respectively, by contacts 51, 52 and 53.

The receiving printing magnets for channel 1 are shown enclosed in rectangle 76 and those for channel 2 in rectangle 77. Each of t-he five magnets in channel 1 has one of its terminals connected to a segment in receiving ring 27 and its other terminal connected to positive battery, whereas the magnets in channel 2 have their common terminal connected to negative battery. The magnets in channels 3 and 5 are connected to positive battery like channel 1 and the magnets in channel 4 have their common terminal connected to negative battery, like channel 2. When transmitting tongues in channels 1, 3 and 5,at the distant station (station A) are in their normal positions, they will send only positive impulses, whigh will notv affect the receiving printers at station B in those channels since their common return is also connected to positive battery. Likewise, channels 2 and 4at station A will transmit only negative impulses which will not affect the printers in those channels at station B, since their common return is connected to negative battery. Hence, whenever the transmitting tongues lie on their left contacts, as shown in the drawings, the impulses transmitted will have no effect on the receiving printers. Cams 37, 38, 36 and 39 mounted on shaft 57 control the operation of contacts for performing in proper sequenceditferent switching operations necessary to change the apparatus from the sendingto receiving condition, or vice versa. Shaft 57 is driven from motor 44 through a friction clutch 43 under the control of the escapement mechanism comprising escapement wheel 40 and magnet 42, which operates under the joint control of timing rings 14 and 15 on the distributor, and cam 58. A clear conception of this invention can now best be obtained by following through in detail the actual functioning of the apparatus during a reversal of the direction of. transmission. 'With the apparatus in the 'drawing in receiving position as shown, and identical station A at the distant end of the cable transmitting, received impulses arrive over the'cable, pass through the armature 4 and contact 5 of switching relay 2 to the rece1ving shaping network and amplifier 6, 105 where they are corrected and amplified and thereafter operate receiving relay 8.and corrector relay 9. The armature of relay 9 vibrates on each reversal of current and in turn transmits a current reversal to the synchronous corrector mechanism 12. If station B is in phase with station A, these reversals will produce no effect in the 'synchronous corrector mechanism, but whenever station B gets slightly out of phase with station Athe reversals cause mechanism 12 to step the main drive shaft 65 backward or forward, as required to restore synchronism, by means of theworm 13, gear 8O and differential 62.

The current reversals through relay 8.actuate its armature 10 to contact with positive .and negative battery in accordance with the vcharacter of the received signals and thus length of which is determined by the rate of IOta'On of cam 67, whichis driven at reduced 13"' Hence shaft 57 will continue to rotate, under control of magnet 42, until contacts 58 are again opened by a rotation of the shaft 57 through 180,9, During-this rotation cam 37 first operatesl to open contacts'48 and cut off the receiving printer. Thereafter cam 36 operates to transfer'contact 55 from the connection to positive battery' on contact 56 to the connection to negative battery on contact 54,

L which reverses the position of relay 2 and connects cable conductor 1 through contact 3 and sending shaped network 7 to the sending distributor ring 17. The transmitting tongues of the transmitters are in their normal posit-ion at this time because the transmitter control magnets, as represented by 21 in channel 1, are locked up through the operation of the 'differential relays, since the transmitter control contacts 49 to 53, respectively, are held open by.cam 38. Thus, While the transmitting brush 17 is passing over the segments of channels 1, 3 and 5, only positive impulses are transmitted to the line, and when passing over the segments of channels 2 and 4 only negative impulses are transmitted to the line. As pointed out before, these impulses will not operate the associated printing mechanisms at station A, but the current reversals which occur as the brush 17 passes from channel 1 to channel 2., from channel 2 to channel 3, from channel 3 to channel 4, and from channel 4 to channel 5, will cause reversals of the synchronizing corrector relay 9 at station A and will bring the A distributors at that station back into proper phase relation with the distributors at sta'- t-ion B if any relative 'displacement may have occurred since thedirection of transmission was reversed by cams 36 at each station.

'lVhen the shaft 57 has rotated through 180 cam 38 operates to close transmitter control contacts 49 to 53, respectively, which releases the locking magnets 21 andy permits the transmission of signal' impulses. The period of time between the operation of the 'direction reversing magnet by cam 36 and the closure of contacts 49 to 53 by cam 38 affords suii`1- cient time to fully correct the distant station to synchronism with station B before the resumption of signal transmission. In practice, the total time required for a half-revov lution of shaft 57 may be in the neighborhood of Vsiii seconds, and the synchronizing time bctween the operation of switch 55 by'cam .36A

and the operation of switches 49 to 53 by cam 38 may be about four seconds.

Station B will now continue to transmit sign al impulses until cam 67 has completed a revolution, when it will again close contacts 68 to begin the rotation of sha-ft 57 under the control of contacts 58 and the connected segments on ring 16. mmediately shaft 57 begins to rotate, cam 38 opens the contacts 49 to 53, respectively, which locks up the transmitters after each has transmitted a signal impulse, under the control of brush 85. For a brief period thereafter. the transmitters send spacing impulses, which have no eii'ect on the printers at station A, until the rotation of cam 36 again moves contact 55 from connection with negative battery to connection with positive battery and reverses theposition of line switch relay 2 to disconnect the cable conductor from the sending distributor and connect it to the receivingshaping network and amplifier.- -At the same time the reversing relay at station A has connected the cable conductor 1 to the sending distributor vat that stationwhich thereupon transmits spacing impulses in the same fashion that station B did during the first half of the sendrcceive cycle. These spacing impulses actu- `atc relays`8 and 9), but they are prevented from operating the receiving printers because the contacts 48 operated by cam 37 are open, which disconnects armature 1() of relay 8 :from the common ring 26 ofthe receiving'distributor. Relay 9, however, vibrates in response to received channel current reversals and repeats reversals over the conductor 11 to the synchronous corrector mechanlsm 12,

causing it to properly orient shaft 65 and' shaft 64. This correcting period obtains until shaft. 57 has almost completed its halfrevolution when cam 37 closes contacts 48 and ,received impulses from the line relay 8 are transmitted to the sending-receiving ring 26. Cam 37, as shown, connects the recclving distributor to the line relay slightly before cam 38 at station A connects thej impulse transmitters at. that station. This is to-insure that signal transmission will not be begun before the receiving equipment is connected to the line. This early connection of the receiving distributor is permissible because at that time the two stations are in phase and the distant station is transmitting only spacing impulses, which will have no effect on the receiv- 4tion and transmitting synchronizing impulses only, lfor a brief period followingeach reversal of the direction of transmission and preceding the transmission of signal impulses.

2. In synchronous telegrapliy, the method of signaling which comprises transmitting` signal impulses and utilizing them at a remote point for both signaling and synclironizing purposes, reversing the direction of transmission and preventing the transmission or reception of signal impulses for a period of time during which synclironizing impulses are transmitted and received for synchronizing purposes and thereafter transmitting and receiving signal impulses for both signaling and synchronizing purposes.

3. In a synchronous telegraph system com-l prising a line conductor, a transmitter and a receiver at each terminal thereof,

' switching means operating to connect the 'transmitter at one terminal to said conductor and to cause the transmitter to trans- A mit spacing impulses for a period of time and thereafter to transmit signal impulses. 4. In a synchronous telegraph system, a

line conductor, a transmitter adapted toV transmit special `synchronizing impulses,

- or signaling impulses, J at one terminal thereof,l a receiver at the distant end of the conductor comprising signal recording apparatus responsive only to signaling impulses and synchronism correcting apparatus responsive to both the special synchronizing impulses and to the signaling impulses transmitted by said transmitter, switching means to connect the transmitter and the receiver'to the conductor terminals and to cause the transmitter to transmit only synchronizing im ulses for a period of time thereafter, whereby theI receiver is synchronized with the transmitter, and thereafterl cause the transmitter to transmit signal impulses.

5. A system as defined in claim 4, characterized in that said switching means also I operates to prevent the ^functioning of said signal recording apparatus until the transmitter is conditioned to transmit signal iinpulses.

6. In a synchronous telegraph system; a line conductor, a transmitter anda receiver at each 1 terminal thereof, each transmitter being adapted to transmit special synchronizing impulses or signaling impulses, and

each .receiver comprising signal recording apparatus responsive only to signaling impulses, and synchronism correcting apparatus responsive to both the special synchronizing impulses and to the signaling impulses transmitted by a transmitter, switching means at each terminal of a conductoradapted to periodically reverse the 7. In a synchronous telegraph system, aA

lineconductor, a synchronous transmitter comprising distributor segments `with impulse transmittersconnected thereto, means for locking said impulse transmitters whereby they are prevented from transmitting signal impulses and caused to transmit only spacing impulses, -a receiver comprising distributor segments connected to automatic printing apparatus adapted to be locked whereby it cannot respond to received impulses, and synchronous correcting apparatus responsive to hotli spacing impulses and `to signal impulses, switching means operating to connect said transmitter segments to the line conductor and to lock said impulse transmitter whereby only spacing impulses are transmit-ted for a period of time and to subsequently release said impulse transmitter whereupon signal impulses are transmitted, said switching means also operating to lock said-printer at the receiving station while spacing impulses are transmitted.

In witness whereof, I here-unto subscribe my name this 9th day of'July, A. D., 1927.

esoneri A. Locirn. 

